The present invention relates generally to textile yarn spinning methods and apparatus and, more particularly, to a method and apparatus for automatically exchanging roving bobbins in spinning apparatus of the type wherein yarn is spun from roving.
The textile yarn spinning apparatus to which the present invention relates may be ring spinning machines, spinning or twisting machines, cop spinning machines or can spinning machines in particular, although the present invention has applicability to other types of spinning machines as well. In such spinning machines, a plurality of yarn spinning stations are fed with roving supplied from a plurality of roving bobbins removably supported in a bobbin creel or the like. Conventionally, plate-like carriers, which are selectively mountable to and demountable from the bobbin creel, are utilized for pivotably suspending the roving bobbins in groups. In such creel arrangements, an automatic bobbin changing apparatus may be compatibly utilized for removing the bobbin carriers once the bobbins thereon are spent and exchanging a substitute carrier having a group of full bobbins. A representative example of such bobbin exchanging apparatus is disclosed in European Patent No. 62 063. A photoelectric scanner may be utilized to detect the exhaustion of the roving bobbins on each carrier and to actuate automatic operation of the bobbin exchanging apparatus to replace the carrier with a carrier containing full bobbins.
Ordinarily, the several roving bobbins grouped on a carrier will not exhaust their respective roving supplies simultaneously even though the unwinding of roving therefrom was begun simultaneously. Thus, a number of the spinning stations associated with each group of roving bobbins will typically be out of operation for varying periods of time after their associated roving bobbins empty while awaiting the next exchange of roving bobbins. As will be understood, this down time results in considerable losses in spinning production.
Another potential problem with the aforedescribed bobbin carriers is the risk that the carriers may sometimes be imprecisely or improperly positioned on the spinning machine which can result in breaks in the roving. Frequent roving breaks may also be caused by a poor quality of roving which, for example, may result from the intermittently faulty operation of the roving fly frame or other roving producing machine. As will be understood, breaks in the roving can cause extended down time and production losses at the respective spinning stations. Particularly, while it would be desirable to exchange roving bobbins in such situations in which frequent roving breaks occur, such roving breaks may remain unnoticed for extended times since the photoelectric sensors associated with an automatic bobbin exchanging apparatus will continue to detect the presence of roving and therefore will not actuate a roving bobbin exchange procedure.
Other potential problems in spinning apparatus may be associated with the yarn piecing devices which are commonly arranged as traveling carriages for movement along the plurality of spinning stations to automatically locate and correct yarn breakages occurring thereat. It is not unusual that such yarn piecing carriages may be unable to successfully correct a yarn break for various reasons. For example, a break in the roving feed to the spinning machine drafting system, the unintended wrapping of the roving around a drafting roller, the breakage of the spinning ring traveler, as well as many other occurrences, may prevent the yarn piecing carriage from performing its normal piecing operation. Accordingly, yarn piecing carriages are conventionally designed to make only a predetermined limited number of attempts, e.g. two or three attempts, to locate and piece a yarn break at any given spinning station. In the event the yarn break cannot be corrected by these attempts, the yarn piecing carriage is programmed to proceed to other spinning stations to eliminate yarn breaks thereat. Otherwise, as will be understood, the yarn piecing carriage would remain continuously at the spinning station having the uncorrectable yarn break. Such yarn piecing carriages are also programmed to record the identity of spinning stations having an uncorrectable yarn break (commonly referred to as "down" or "dead" spinning stations) so that the carriage does not again stop at such spinning station or stations as its traveling operational movement progresses. Such a yarn piecing system is disclosed in German Published Patent Application No. 24 54 721.
As will thus be understood, the occurrence of roving breaks such as described above will ultimately result in the detection of a yarn break at the associated spinning station with an attendant inability of an associated yarn piecing carriage to correct the detected yarn break. When a significant number of the roving bobbins in any given carrier group experience roving breaks, such as due to an improper positioning of the carrier or to defective roving, the corresponding spinning stations will each experience an uncorrectable yarn break while at the same time the bobbin exchanging apparatus will remain inactive since the roving bobbins will not have been spent. As a result, the spinning stations involved will remain down for an extended period of time with an attendant loss of production.